scholarly journals Full inversion of solar relativistic electron events measured by the Helios spacecraft

2019 ◽  
Vol 624 ◽  
pp. A3 ◽  
Author(s):  
D. Pacheco ◽  
N. Agueda ◽  
A. Aran ◽  
B. Heber ◽  
D. Lario
Keyword(s):  
Relativistic Electron ◽  
Free Path ◽  
Transport Model ◽  
Radial Distance ◽  
Mean Free Path ◽  
Time Profile ◽  
Release Time ◽  
The Sun ◽  
Data Set ◽  
Energy Channel

Context. The Parker Solar Probe and the incoming Solar Orbiter mission will provide measurements of solar energetic particle (SEP) events at close heliocentric distances from the Sun. Up to present, the largest data set of SEP events in the inner heliosphere are the observations by the two Helios spacecraft. Aims. We re-visit a sample of 15 solar relativistic electron events measured by the Helios mission with the goal of better characterising the injection histories of solar energetic particles and their interplanetary transport conditions at heliocentric distances <1 AU. Methods. The measurements provided by the E6 instrument on board Helios provide us with the electron directional distributions in eight different sectors that we use to infer the detailed evolution of the electron pitch-angle distributions. The results of a Monte Carlo interplanetary transport model, combined with a full inversion procedure, were used to fit the observed directional intensities in the 300–800 keV nominal energy channel. Unlike previous studies, we have considered both the energy and angular responses of the detector. This method allowed us to infer the electron release time profile at the source and determine the electron interplanetary transport conditions. Results. We discuss the duration of the release time profiles and the values of the radial mean free path, and compare them with the values reported previously in the literature using earlier approaches. Five of the events show short injection histories (<30 min) at the Sun and ten events show long-lasting (>30 min) injections. The values of mean free path range from 0.02 AU to 0.27 AU. Conclusions. The inferred injection histories match with the radio and soft X-ray emissions found in literature. We find no dependence of the radial mean free path on the radial distance. In addition, we find no apparent relation between the strength of interplanetary scattering and the size of the solar particle release.

scholarly journals Diffusive transport of energetic electrons in the solar corona: X-ray and radio diagnostics

2018 ◽  
Vol 610 ◽  
pp. A6 ◽  
Author(s):  
S. Musset ◽  
E. P. Kontar ◽  
N. Vilmer
Keyword(s):  
Solar Corona ◽  
Free Path ◽  
Electron Distribution ◽  
Transport Model ◽  
Imaging Spectroscopy ◽  
Mean Free Path ◽  
Diffusive Transport ◽  
X Rays ◽  
Energetic Electrons ◽  
X Ray

Context. Imaging spectroscopy in X-rays with RHESSI provides the possibility to investigate the spatial evolution of X-ray emitting electron distribution and therefore, to study transport effects on energetic electrons during solar flares. Aims. We study the energy dependence of the scattering mean free path of energetic electrons in the solar corona. Methods. We used imaging spectroscopy with RHESSI to study the evolution of energetic electrons distribution in various parts of the magnetic loop during the 2004 May 21 flare. We compared these observations with the radio observations of the gyrosynchrotron radiation of the same flare and with the predictions of a diffusive transport model. Results. X-ray analysis shows a trapping of energetic electrons in the corona and a spectral hardening of the energetic electron distribution between the top of the loop and the footpoints. Coronal trapping of electrons is stronger for radio-emitting electrons than for X-ray-emitting electrons. These observations can be explained by a diffusive transport model. Conclusions. We show that the combination of X-ray and radio diagnostics is a powerful tool to study electron transport in the solar corona in different energy domains. We show that the diffusive transport model can explain our observations, and in the range 25–500 keV, the scattering mean free path of electrons decreases with electron energy. We can estimate for the first time the scattering mean free path dependence on energy in the corona.

scholarly journals Session IV: Open Discussion

1971 ◽  
Vol 2 ◽  
pp. 239-243
Keyword(s):  
Angular Momentum ◽  
Free Path ◽  
Mean Free Path ◽  
Statistical Investigation ◽  
The Sun ◽  
Planetary Formation ◽  
Retrograde Orbit ◽  
Open Discussion ◽  
The Mean ◽  
Gas Cloud

The Chairman, J. S. Hall asked I. P. Willams (Reading, England) to speak on ‘Planetary Formation’.Williams: According to a theory by McCrea, published in 1960, after a protosun has been formed about 1000 unstable cloudlets, called floccules by McCrea, are captured in orbit around this protosun. Their orbital distance is roughly equal to the mean free path of the floccules in the original gas cloud from which both the sun and the captured floccules formed, taken numerically to the 60 AU. In order to conserve angular momentum about 600 of the captured floccules will be in prograde orbit while 400 will be in retrograde orbit. As an agglomeration of about 20 floccules is stable, when floccules adhere on collision stable condensations may be formed. We make a statistical investigation of this process. The problem is similar to that of having 400 red balls and 600 black balls in a bag which are pulled out and assembled into a pile. When 20 are in a pile a stable condensation exists and a new pile is started. If there are equal numbers of red and black balls in a pile this compounds to a condensation with very low angular momentum which falls into the Sun and so this is rejected and a new pile started. The number of stable condensations that is formed and the ratio of prograde to retrograde floccules in each of these condensations are obtained. This ratio determines the angular momentum, and hence the position, of the condensation.

SIMULATION OF THE TRANSITION BETWEEN MESON-SYSTEM AND QGP IN A TRANSPORT MODEL

2007 ◽  
Vol 16 (07n08) ◽  
pp. 2269-2275 ◽  
Author(s):  
ZHIGUANG TAN ◽  
ALDO BONASERA ◽  
CHUBIN YANG ◽  
DAIMEI ZHOU ◽  
S. TERRANOVA
Keyword(s):  
Free Path ◽  
Finite Temperature ◽  
Transport Model ◽  
Mean Free Path ◽  
Bag Model ◽  
Thermodynamical Properties ◽  
Model Based ◽  
Mit Bag Model ◽  
The Mean ◽  
Meson System

Some thermodynamical properties of the interacting meson system and QGP at finite temperature are discussed. For a pure meson gas the Hagedorn limiting temperature is reproduced when the experimentally observed resonances are included. For QGP our results for different numbers of flavors Nf compare very well to the theoretical ones. A transport model based on the mean free path approach is used to simulate the evolution of the system. During the evolution we use the MIT bag model to perform the transition between meson gas and QGP.

scholarly journals Cross-field gradients: general concept, importance of multi-spacecraft measurements and study at 1 AU of the source intensity gradient for E > 30 keV solar event electrons

2000 ◽  
Vol 18 (3) ◽  
pp. 263-276
Author(s):  
P. A. Chaizy
Keyword(s):  
Solar Physics ◽  
Radial Distance ◽  
Onset Time ◽  
Mean Free Path ◽  
General Concept ◽  
Angular Distance ◽  
Transport Processes ◽  
The Sun ◽  
Time Profiles ◽  
Field Gradients

Abstract. Three main physical processes (and associated properties) are currently used to describe the flux and anisotropy time profiles of solar energetic par- ticle events, called SEP profiles. They are (1) the particle scattering (due to magnetic waves), (2) the particle focusing (due to the decrease of the amplitude of the interplanetary magnetic field (IMF) with the radial distance to the Sun) and (3) the finite injection profile at the source. If their features change from one field line to another, i.e. if there is a cross IMF gradient (CFG), then the shape of the SEP profiles will depend, at onset time, on the relative position of the spacecraft to the IMF and might vary significantly on small distance scale (e.g. 106 km). One type of CFG is studied here. It is called intensity CFG and considers variations, at the solar surface, only of the intensity of the event. It is shown here that drops of about two orders of magnitude over distances of ~104 km at the Sun (1° of angular distance) can influence dramatically the SEP profiles at 1 AU. This CFG can lead to either an under or overestimation of both the parallel mean free path and of the injection parameters by factor up to, at least, ~2-3 and 18, respectively. Multi-spacecraft analysis can be used to identify CFG. Three basic requirements are proposed to identify, from the observation, the type of the CFG being measured.Key words: Solar physics, astrophysics, and astronomy (energetic particles; flares and mass ejections) - Space plasma physics (transport processes)

scholarly journals KINETIC DESCRIPTION OF HADRON–HADRON COLLISIONS

2008 ◽  
Vol 17 (08) ◽  
pp. 1577-1589 ◽  
Author(s):  
ZHI GUANG TAN ◽  
S. TERRANOVA ◽  
A. BONASERA
Keyword(s):  
Energy Density ◽  
Free Path ◽  
Transport Model ◽  
Mean Free Path ◽  
Critical Value ◽  
Kinetic Description ◽  
Pp Collisions ◽  
High Energies ◽  
Mit Bag Model ◽  
The Mean

A transport model based on the mean free path approach to describe pp collisions is proposed. We assume that hadrons can be treated as bags of partons similarly to the MIT bag model. When the energy density in the collision is higher than a critical value, the bags break and partons are liberated. The partons expand and can coalesce to form new hadrons. The results obtained compare very well with available data, and some predictions for higher energies collisions are discussed. Based on the model we suggest that a QGP could already be formed in pp collisions at high energies.

scholarly journals Landauer-Datta-Lundstrom Generalized Transport Model for Nanoelectronics

2014 ◽  
Vol 2014 ◽  
pp. 1-15 ◽  
Author(s):  
Yuriy Kruglyak
Keyword(s):  
Electron Transport ◽  
Band Structure ◽  
Free Path ◽  
Power Law ◽  
Linear Response ◽  
Transport Model ◽  
Transport Coefficients ◽  
Mean Free Path ◽  
Linear Dispersion ◽  
Thermoelectric Transport

The Landauer-Datta-Lundstrom electron transport model is briefly summarized. If a band structure is given, the number of conduction modes can be evaluated and if a model for a mean-free-path for backscattering can be established, then the near-equilibrium thermoelectric transport coefficients can be calculated using the final expressions listed below for 1D, 2D, and 3D resistors in ballistic, quasiballistic, and diffusive linear response regimes when there are differences in both voltage and temperature across the device. The final expressions of thermoelectric transport coefficients through the Fermi-Dirac integrals are collected for 1D, 2D, and 3D semiconductors with parabolic band structure and for 2D graphene linear dispersion in ballistic and diffusive regimes with the power law scattering.

Inelastic mean free path and phase-shift determinations in NiO, using EXELFS

1993 ◽  
Vol 3 (7) ◽  
pp. 1649-1659
Author(s):  
Mohammad A. Tafreshi ◽  
Stefan Csillag ◽  
Zou Wei Yuan ◽  
Christian Bohm ◽  
Elisabeth Lefèvre ◽  
...  
Keyword(s):  
Phase Shift ◽  
Free Path ◽  
Mean Free Path ◽  
Inelastic Mean Free Path
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